OBBBA AMT Changes 2026: New Thresholds, Doubled Phase-Out Rate, and Who Gets Hit

The One Big Beautiful Bill Act (OBBBA) made the alternative minimum tax meaningfully harder to avoid for clients in the $500,000–$1,300,000 income range. Starting in 2026, the AMT exemption phase-out threshold drops sharply — from $626,350 to $500,000 for single filers — and the phase-out rate doubles from 25 to 50 cents per dollar. The net result is that clients who comfortably cleared AMT in prior years now face meaningful exposure, and clients who had a partial AMT cushion no longer have one. Every CPA with high-income W-2 earners, ISO holders, real estate investors, or S-Corp owners in that income band needs to update their AMT screening process before Q3 estimated payment time.

What the OBBBA Changed About AMT

The individual AMT, governed by IRC §§55–59, operates through a parallel income calculation that adds back certain deductions and preference items, then applies a flat rate (26% on the first $239,900 of AMTI, 28% above). Taxpayers pay whichever is higher — regular tax or the tentative minimum tax. A generous exemption (and corresponding phase-out) largely shields most taxpayers; the OBBBA changed both the exemption base and how fast it evaporates.

Three specific changes took effect for 2026:

1. Exemption base reverts to 2018 levels, then inflation-adjusts forward. The TCJA significantly raised AMT exemptions and applied inflation adjustments annually from 2018 through 2025. The OBBBA resets the base to 2018 values and restarts the inflation adjustment from there — creating a one-time step backward before resuming forward indexing. After the 2026 inflation adjustment, single filer exemptions land at approximately $90,100 and MFJ exemptions at approximately $140,200. These are modestly higher than 2025 ($88,100 single / $137,000 MFJ), but the threshold changes below swamp the exemption increase.

2. Phase-out thresholds drop sharply. Under the OBBBA, the AMT exemption begins phasing out at $500,000 AMTI for single filers (down from $626,350 in 2025) and $1,000,000 for MFJ (down from $1,252,700). The exemption phases out completely at $680,200 for singles (down from $978,750) and $1,280,400 for MFJ (down from $1,800,700). A single filer with $700,000 AMTI had approximately $69,700 of remaining AMT exemption in 2025 — the same client has zero exemption in 2026.

3. Phase-out rate doubles. The OBBBA doubles the rate at which the exemption phases out: from 25 cents per dollar of AMTI above the threshold to 50 cents. This cuts the phase-out range in half (from ~$352,000 to ~$180,200 for singles), meaning the exemption disappears twice as fast as income rises above the threshold.

Verify 2026 exemption amounts with IRS inflation adjustments published in Rev. Proc. 2025-xx or Notice 2025-xx before filing.

Who Gets Newly Exposed in 2026

The clients most affected are those in the income bands where the threshold changes have the largest impact.

Single filers with AMTI of $500,000–$626,350. Under 2025 rules, these clients hadn't reached the phase-out threshold at all — they kept their full $88,100 exemption. Under 2026 OBBBA rules, they're now in the phase-out zone. A client at $560,000 AMTI loses ($560,000 - $500,000) × $0.50 = $30,000 of exemption, leaving only $60,100. Depending on their regular tax liability, this can mean an unexpected AMT bill.

Single filers with AMTI of $626,350–$978,750. These clients were in the phase-out zone in 2025 but retained a partial exemption. In 2026, anyone above $680,200 has a zero exemption — a $700,000 filer who had ~$69,700 of exemption cushion now has none.

MFJ filers with AMTI of $1,000,000–$1,252,700. Same story for joint filers. Under 2025 rules they hadn't reached the phase-out threshold. In 2026 they're in the zone.

MFJ filers with AMTI of $1,252,700–$1,800,700. Partial exemption in 2025, zero exemption for the higher part of this range in 2026.

Practically, the types of clients most likely to land in these affected bands:

• ISO holders who exercise incentive stock options in 2026 — the bargain element (FMV minus exercise price) is an AMT preference item under IRC §56(b)(3), and ISO exercises in a year of otherwise elevated income can push a client into the new phase-out zone
• S-Corp owners with a high-distribution year or a sale event landing between $500K and $680K
• Real estate investors with large depreciation recapture or a property sale year generating unrecaptured §1250 gain
• High-income professionals in the $500K–$700K W-2 range who previously had no AMT exposure due to the SALT deduction offsetting regular tax (but SALT is disallowed for AMT)

The AMT Disallows the SALT Deduction — a Critical Interaction

The OBBBA raised the SALT cap to $40,000 (phasing out above $500,000 MAGI) for 2025–2029. This matters for AMT planning because the AMT system does not allow a SALT deduction at all — state and local taxes are added back as an AMT adjustment item. A client who counts on a $30,000 SALT deduction to reduce their regular tax receives zero benefit from that deduction if they're paying AMT.

The implication: clients in states with high income taxes who were relying on the new $40,000 SALT cap to reduce their regular tax burden may still face AMT if their income falls in the new $500K–$680K zone. The SALT deduction reduces regular tax only, making AMT more likely to apply. This is a planning error to catch proactively — the SALT cap planning strategies that reduce regular tax may simultaneously increase AMT exposure.

Planning Strategies for the New AMT Environment

1. Update your AMT screening to start at $500,000. In 2025 the screening threshold for single filers was effectively $626,350. That is now $500,000. Every client with projected AMTI between $500,000 and $700,000 deserves an AMT model before the first Q3 estimated payment. Build this into your mid-year review process.

2. Model ISO exercise timing against the new thresholds. ISO exercises have historically been one of the most reliably AMT-triggering events. With the lower phase-out threshold, exercises that were AMT-neutral in 2025 may not be in 2026. Clients who hold unexercised ISOs and have projected income above $500,000 should review exercise timing with both the income and AMT calculations in hand. The disqualifying disposition strategy (selling ISOs the same year they are exercised) converts the gain to ordinary income but avoids the AMT preference item — worth modeling when the AMT bite is large.

3. Identify and utilize minimum tax credit carryforwards. AMT paid in prior years creates a minimum tax credit (MTC) that can be used against regular tax in future years when regular tax exceeds tentative minimum tax — tracked on Form 8801. Many clients have unused MTC from prior ISO exercises or other AMT-generating events. With the 2026 changes pushing more clients into AMT, clients who paid AMT pre-TCJA (2016 and before) may have significant accumulated MTC from years before the TCJA exemption increases. This credit doesn't expire and can offset regular tax dollar-for-dollar in appropriate years.

4. Evaluate private activity bond (PAB) exposure. Interest income from tax-exempt bonds issued to fund private projects — private activity bonds — is a preference item added back to AMTI under IRC §57(a)(5). Clients holding PAB-heavy municipal bond funds who didn't face AMT in 2025 due to the higher exemption thresholds may face it in 2026. Review bond fund prospectuses for PAB percentage disclosures.

5. Accelerate income above $680,200 rather than stopping just below. Counterintuitively, a client at $650,000 AMTI (still in the phase-out zone, paying AMT) can sometimes improve their tax position by recognizing additional income to push above $680,200 — above which the exemption is zero anyway but regular tax rates may produce a better effective rate than the AMT rate. This depends entirely on the specific rate comparison and should be modeled, not assumed.

6. Coordinate with NIIT planning. Both NIIT and AMT are triggered by investment income. Strategies that reduce net investment income (converting passive income to active, real estate professional classification, installment sale elections) also reduce the AMTI base, potentially preserving more of the AMT exemption. Treat NIIT and AMT planning as a combined exercise for clients in the affected income range.

The AMT Credit: Don't Leave It on the Shelf

When a client pays AMT, the difference between their AMT liability and their regular tax liability becomes a minimum tax credit. That credit is not lost — it carries forward indefinitely and offsets regular tax in future years when regular tax exceeds tentative minimum tax (Form 8801). Clients who have paid AMT in any year, including pre-TCJA years, may have substantial accumulated credits that go unreported because the preparer switched after the TCJA exemption increases made clients AMT-free.

Pull every client's prior-year returns back to at least 2016 and verify whether Form 8801 credit carryforwards exist. For clients now heading back into AMT territory in 2026, this credit will be immediately useful — potentially offsetting AMT dollar-for-dollar in the first year regular tax again exceeds tentative minimum tax.

Frequently Asked Questions

Does the OBBBA AMT change affect C-Corps?

No. The corporate AMT was permanently repealed by TCJA in 2018 and the OBBBA did not reinstate it. A separate corporate alternative minimum tax (15% book minimum tax) applies to corporations with average annual adjusted financial statement income exceeding $1 billion under the Inflation Reduction Act of 2022, but that does not apply to S-Corps or most privately held businesses. The OBBBA changes described in this article apply only to the individual AMT under IRC §55.

If my client paid AMT in 2025 under the old rules, does the new 2026 law change how they calculate their Form 8801 credit?

No. The minimum tax credit carryforward is based on prior-year AMT paid and carries forward at the dollar amount actually paid. The 2026 law changes the thresholds and rates for computing current-year AMT, not how prior-year credits are calculated or utilized. Prior AMT paid flows directly to Form 8801 and offsets regular tax in future years.

Does the SALT cap increase under OBBBA help with AMT?

No. The $40,000 SALT cap increase applies only to the regular income tax calculation. SALT deductions are completely disallowed for AMT purposes regardless of how large or small the SALT cap is for regular tax. The two systems run in parallel — a $40,000 SALT deduction reduces regular taxable income but adds back to AMTI in full.

Are long-term capital gains taxed at AMT rates?

Preferentially taxed income — long-term capital gains and qualified dividends — retains its preferential rates (0%, 15%, or 20%) within the AMT calculation. However, capital gains can increase AMTI (and thus push more ordinary income into the AMT zone), even though the gains themselves are not taxed at the 26%/28% AMT rate. A large capital gains year that raises AMTI into the phase-out zone effectively increases the AMT rate on the client's other income by reducing or eliminating the exemption.

What happens to a client who exercises ISOs in 2026 and then the stock drops before year-end?

This is the classic ISO AMT trap. The bargain element at exercise is an AMT preference item in the year of exercise, even if the stock later declines. If a client exercises ISOs in 2026 and the stock drops below the exercise price before year-end, they face AMT on phantom income they never realized. Disqualifying dispositions (selling before the holding period qualifies) eliminate the preference item but convert the gain to ordinary income. The decision should be modeled early in the year based on projected income and the new 2026 phase-out thresholds, not after the year has passed.

How does the doubling of the phase-out rate affect planning compared to prior years?

The practical effect is that the "AMT island" — the income range where a client is in partial phase-out and might benefit from income shifting to stay below the threshold — is now much narrower (approximately $180,200 for singles vs. $352,000 in 2025). It is harder to plan around because there is less room to work with. Clients just above $500,000 might benefit from modest income deferral; clients above $680,200 are in full AMT territory and the focus shifts to minimizing preference items rather than threshold management.

CPAs navigating AMT exposure alongside the broader OBBBA itemized deduction changes should model both calculations together — the deduction limitations that reduce regular tax can simultaneously increase AMT exposure for clients in the affected range. Arvori's platform surfaces these interactions in client advisory workflows so CPAs can model the full picture without running multiple separate projections.